BULLETIN OF MARINE SCIENCE, 40(3): 428-436, 1987

A NEW SPECIES OF (OPISTHOBRANCHIA: ) FROM THE CARIBBEAN SEA

Terrence M. Gosliner and Michael T. Ghiselin

ABSTRACT The tritoniid opisthobranchs of the western Atlantic have recently been reviewed (Marcus, 1983). Seven species in three or four genera are known from tropical and subtropical waters of the region. Investigations by one of us (M.T.G.) in the Bahamas yielded specimens of what appeared to be an undescribed species of Tritonia. Subsequently, our joint investigations in Quintana Roo, Mexico have provided additional specimens of this species. This paper de- scribes the anatomy of this new species and compares it to closely allied species.

DESCRIPTION Tritonia ham nerorum new species

Type Material. - Holotype: Department ofInvertebrate Zoology, California Academy of Sciences, San Francisco, CASIZ 061278, near La Ceiba Hotel, Puerto Morelos, Quintana Roo, Mexico, on Gorgonia flabellum Linnaeus, 2 m depth, 27 March 1985, collected by T. M. Gosliner. Paratypes.-CASIZ 061279, 87 specimens, near La Ceiba Hotel, Puerto Morelos, Quintana Roo, Mexico, on Gorgoniaflabellum, 2 m depth, 27 March 1985, collected by T. M. Gosliner. Paratypes.-CASIZ 061280, 14 specimens, Sandy Cay, Great Abaco Island, Bahamas, on Gorgonia flabellum, 4 m depth, 16 July 1983, collected by M. T. Ghiselin. Etymology. - This species is named for William and Peggy Hamner, who accom- panied one of us (M.T.G.) while collecting the specimens in the Bahamas. External Morphology. - The living (Figure I) reach IS mm in length. The notum is smooth, devoid of tubercles. The ground color of living specimens is light pinkish purple, the same color as their gorgonian prey. Extending the length of the notum are a series of approximately 20 opaque white longitudinal lines. The lines are irregular with some short interconnecting lines. The gills, rhinophores and velar tentacles are tipped with opaque white. The preserved specimens (Fig. 2) reach 11 mm in length. The semi-circular velum (Fig. 3) contains 2-3 pairs of velar tentacles, including the outermost, which are the oral tentacles. In some cases there are only two tentacles on one side and three on the other. The rhino- phores (Fig. 4) contain a series of simple or slightly pinnate digitiform lobes, surrounding the cylindrical apical papilla. In five specimens examined there are nine slightly pinnate gills (Figs. 2, 5) on each side of the body. There are 5-7 irregular lobes on the rhinophore sheath. The outer lobe is largest and triangular in shape. The anus (Fig. 2) is situated between the third and fourth gills, on the right side of body, ventral to the notal brim. The nephroproct is immediately dorsal to the anus. The distinct male and female gonopores, located between the first and second gills, below the notal brim, are well separated from each other. The anterior end of the foot is simply rounded. Digestive System. - The buccal mass is thick and muscular. Well developed oral glands surround the dorsal, lateral and ventral surfaces of the buccal mass. The jaws (Fig. 6) are thin and elongate with a long masticatory border, consisting of about six rows of acutely pointed denticles. The radula (Figs. 7-9) has a formula

428 GOSLINER AND GHISELIN: CARIBBEAN TR1TON1A 429

Figure I. Tritonia hamnerorum new species. Living . of 26-29 x 9-10.1.1.1.9-10., in three specimens examined. The rachidian teeth are tricuspid with an acute central cusp, which is often worn in older teeth. The lateral denticles of the rachidian are broadly triangular. The inner lateral teeth are hook-shaped, with an inner denticle. Their anterior surface bears 5-8 irreg- ularly spaced denticles. In older teeth these denticles may not be present, due to wear. The outer lateral teeth are sickle shaped and become progressively more elongate towards the outer margin. The elongate and strap-like salivary glands join the buccal mass at the junction of the esophagus and buccal mass. The esophagus is narrow, but expands into the stomach as it enters the digestive gland. There are no cuticular plates or ridges within the stomach. Central Nervous System (Fig. IO).-All of the ganglia form a mass on the dorsal surface of the esophagus and buccal mass. The cerebral ganglia are completely fused with the pleurals, and are closely appressed to each other. The pedal ganglia are separated by a short commissure. The buccal ganglia are ventral to the pedal ganglia and are closely appressed to each other. They are situated at the ventral surface of the junction of the esophagus with the buccal mass. Reproductive System (Fig. 11).- The preampullar coelomic gonoduct is narrow and expands into the short, saccate ampulla. The ampulla again narrows into the postampullar gonoduct. After a short distance the gonoduct branches into a short, narrow oviduct and a thicker, non-prostatic vas deferens. The oviduct enters the female gland mass near the albumen gland. The small membrane gland is adjacent and distal to the albumen gland. The large mucous gland makes up the bulk of the reproductive system. The receptaculum seminis is spherical and muscular. It joins the mucous gland at the female aperture by means of a narrow duct of moderate length. The non-prostatic vas deferens widens into a prostatic portion, 430 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.3, 1987

Figure 2, Tritonia hamnerorum new species. Right lateral view of preserved animal; a = anus, f = female aperture, m = male aperture, n = nephroproct; scale = 2.0 mm. Figure 3. TrilOnia hamnerorum new species. Ventral view of head, scale = 1.0 mm. Figure 4. TrilOnia hamnerorum new species. Rhinophore, scale = 0.25 mm. Figure 5. TrilOnia hamnerorum new species. Gill, scale = 0.25 mm.

which enters the proximal end of the penial sac. The short, rounded penial papilla is unarmed, and is contained in a conical penis sac. Egg Mass. - The egg mass, also visible in Figure I, is a white convoluted ribbon that is closely appressed to the surface of the gorgon ian colony. There is a single egg per capsule. Because the veligers have a well-developed velum, they are likely to be planktotrophic. The larval shell is type I (Thompson, 1961). Natural History. -Specimens have been found only in association with the gor- gonian, Gorgonia flabellum Linnaeus. In the Bahamas specimens were found on an attached gorgonian, while the animals from Mexico were found on a detached, but still living, colony. There were 88 individuals of Tritonia hamnerorum present on the single sea fan found in Mexico. GOSLINER AND GHISELIN: CARIBBEAN TRITONIA 431

Figure 6. Tritonia harnnerorurn new species. Scanning electron micrograph of jaw. Figures 7-9. Tritonia harnnerorurn new species. Scanning electron micrographs of radula. 432 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.3, 1987

____e

pr

10

Figure 10. Tritonia harnnerorurn new species. Central nervous system; cp = cerebral pleural ganglion, e = eye, pe = pedal ganglion; scale = 0.5 mm.

Figure II. Tritonia harnnerorurn new species. Reproductive system; al = albumen gland, am = ampulla, f = female aperture, m = male aperture, me = membrane gland, mu = mucous gland, p = penis, pr = prostate, rs = receptaculum seminis; scale = 0.5 mm.

DISCUSSION The separation of genera within the has long been the subject of controversy (Eliot, 1905; Odhner, 1926; 1963; Marcus, 1983). A variety of char- acters have been employed to separate genera, including shape of the rachidian radular tooth, presence or absence of chitinous plates in the stomach, division of the liver (digestive gland), position of the anus, gonopore and nephropore, and shape of the penis. Odhner (1963) attempted to clarify the systematic arrangement of genera in the Tritoniidae. He considered 8 genera with 4 subgenera of Tritonia. Marcus (1983) noted difficulties in clearly differentiating genera. Part of the problem is that different authors have utilized different characters to distinguish genera. Odhner (1963) emphasized that species of Tritoniella are characterized by digitiform processes rather than branched gills along the edge of the notum and have a mid- dorsal ridge. Species in this have an annulation on the tip of the penis. Marcus (1983) included all tritoniids with an annulation around the penis in the genus Tritoniella, including Tritonia festiva (Stearns, 1873) and T. episcopalis Bouchet, 1977. Tritonia diomedea Bergh, 1894, also has an annulation near the apex of its penis (Thompson, 1971, present study). These species have well de- veloped gills and lack a mid-dorsal ridge. It is likely that the presence of a penial annulation is due to parallel evolution of this structure in Tritoniella and in some members of Tritonia. Odhner (1963) distinguished Duvaucelia from Tritonia on the basis of the position of the genital aperture and anus. However, Tritonia hamnerorum new species and T. striata Haefelfinger, 1963 share characteristics of both genera. The anus is in the anterior half of the body (as in Duvaucelia) while the gonopores are GOSLINER AND GHISELIN: CARIBBEAN TR1TON1A 433 posterior to the anteriormost gills (as in Tritonia). Thus the separation of Tritonia and Duvaucelia cannot be maintained. The splitting of Tritonia into subgenera as advocated by Odhner (1963) is not supported by distinct morphological gaps or readily apparent monophyletic groups. Whether the penis is conical or flagel- liform has to be evaluated subjectively and varies considerably within and between species (Thompson, 1971; Marcus, 1983). Similarly, the form of the velum (bi- lobed or entire) and the notum (smooth or with small tubercles) varies between individuals of the same species and is correlated with fixation. Therefore, dis- tinctions between subgenera are artificial and unnecessary. All species of tritoniids with well developed gills, a tricuspid rachidian tooth and without stomach plates are here considered as members of Tritonia. This genus includes large, broad-bodied species such as T. hombergi Cuvier, 1798 (Thompson and Brown, 1984) and small graceful species like T. pickensi Marcus and Marcus, J 967. Within the genus, species may have a broad radula (as in T. eriosi Marcus 1983, which has 160 lateral teeth per half row) or a narrow one (as in T. hamnerorum, which has 9-10 laterals (present study». The shape of the penis, position of the anus and gonopore vary, as discussed above. Tritonia hamnerorum differs significantly from all previously described mem- bers of the genus. The coloration ofthe living animal clearly distinguishes it from other species. Several other species are known to possess opaque white pigment on the notum. Tritonia lineata Alder and Hancock, 1848 has two undulating white lines along the margins of the notum with a branch to each gill (Thompson and Brown, 1984). In T. bayeri Marcus and Marcus, 1967, there is an elaborate network of opaque white lines. Tritonia jestiva (Steams, 1873) has a series of two or three white marginal lines and several ovals in the center of the notum (MacFarland, 1966, present study). Tritonia pickensi Marcus and Marcus, 1967 has a large mid- dorsal patch of opaque white on its notum (Bertsch and Gosliner, 1984). Tritonia hamnerorum is the only species that is known to possess a series of approximately 20 longitudinal lines. Several other aspects of the morphology of T. hamnerorum distinguish it from other members of the genus. Tritonia hamnerorum is compared with the 13 other species of Tritonia that are known from the Atlantic Ocean (Table 1). Of these species, only T. hamnerorum and the two other Caribbean species, T. wel/si Marcus, 1961 and T. bayeri Marcus and Marcus, 1967, possess a fleshy extension on the outer side of the rhinophore sheath. Tritonia hamnerorum appears to be unique among described tritoniids in that there are distinct, well-separated male and female gonopores. Internally, there are several other features that distinguish Tritonia hamnerorum from other members of the genus. Several other species are known to possess denticles on the surface of the inner lateral teeth. In T. plebeia and T. hombergi denticles are present on the inner lateral tooth of juveniles, but are absent in adults (Thompson and Brown, 1984). In T. australis (Bergh, 1898) and T. ni/- sodhneri (Marcus, 1983) a single denticle may be present on the innermost lateral. Tritonia wellsi Marcus, 1961, T. pickensi Marcus and Marcus, 1967, T. bayeri Marcus and Marcus, 1967 and T. hamnerorum all have several denticles on the inner lateral tooth in adult animals. In T. bayeri and T. wel/si there are also denticles on the second lateral, while in T. pickensi and T. hamnerorum the second laterals are always smooth. These four species are also similar in that they have appendages on the rhinophore sheaths and a narrow radula with few lateral teeth. The four species differ significantly in their reproductive morphology. Tritonia pickensi and T. wellsi have an elongate penial papilla, while it is short and conical in T. bayeri and short and rounded in T. hamnerorum. 434 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.3, 1987

Table I. Morphological variability in Atlantic Tritonia

Velar Species Rhinophorc sheath tentacles Gonopore Radular formula australis with series of 6-10 single ventral 40-44 x 44-50.1.1.1.44-50 short lobes to 6th gill bayeri with single 4-6 single between 20-34 x 9-10.1.1.1.9-10 elongate ap- 2nd and 3rd pendage gills challengeriana smooth 8-20 32-43 x 30-45.1.1.1.30-45

episcopalis smooth II single ventral 53 x 74.1.1.1.74 to 2nd gill eriosi with denticulate 16 single ventral 100 x 160.1.1.1.160 appendage to 3rd gill griegi smooth 10-13 single ventral 48 x 98.1.1.1.98 to 4th gill hamnerorum with triangular 4-6 double be- 26-29 x 9-10.1.1.1.9-10 outer lobes tween 1st and smaller and 2nd inner lobes gills hombergi smooth up to 40 single maximum 73 x 229.1.1.1.229

manicata smooth 6-8 single anterior 21-40 x 11-16.1.1.1.11-16 to 1st gill nilsodhneri smooth 6 single ventral 25 x 24-30.1.1.1.24-30 to 1st gill plebeia smooth 4-8 single ventral 20-38 x 32-69.1.1.1.32-69 to 1st gill

striata smooth 4-6 single between 42 x 26.1.1.1.26 1st and 2nd gills wellsi with singular 6 single ventral 20-21 x 10-11.1.1.1.0-11 triangular ap- to 2nd gill pendage

T. hamnerorum, like the majority of species of Tritonia, has an elongate stalk leading to the receptaculum seminis. The receptaculum, in a few species, T. manicata Deshayes, 1839, T. lineata Alder and Hancock, 1848 (Schmekel and Portmann, 1982) and T. nilsodnheri Marcus, 1983 (present study), is sessile or has a very short stalk.

ACKNOWLEDGMENTS

W. Liltved of the California Academy of Sciences kindly prepared the line drawings. We also thank W. and P. Hamner for their assistance in collecting specimens in the Bahamas. We would also like to extend our appreciation to Dr. E. Carillo, Sr. H. Hermann, Sr. M. Angel Ladr6n, Sr. M. Navarro, and the other staff of the Centro de Investigaciones de Quintana Roo, Mexico. Their generosity and . friendship greatly assisted our endeavors.

LITERATURE CITED

Bertsch, H. and T. Gosliner. 1984. Tritonia pickensi (Nudibranchia: Tritoniidae) from Baja Cali- fornia, Mexico. Shells Sea Life 16: 138-139. GOSLINER AND GHISELlN: CARIBBEAN TR/TON/A 435

Table l. Continued

Inncr laterJI 2nd lateral Penis References single denticle smooth conical Odhner, 1926; Marcus, 1983; present study up to 15 denticles 4-5 denticles conical Marcus and Marcus, 1967 smooth smooth conical Odhner, 1926; Marcus, 1983; present study denticulate smooth conical with api- Bouchet, 1977 cal annulation smooth smooth recurved at apex Marcus, 1983 smooth smooth recurved at apex Odhner,1939 with 5-7 denticles smooth short, rounded Present study

denticulate in juve- denticulate in juve- short to elongate Thompson and Brown, niles, smooth in niles, smooth in rounded or coni- 1984 adults adults cal smooth smooth short conical Haefelfinger, 1963 smooth or with one smooth flagelliform Tardy, 1963; present denticle study denticulate in juve- smooth Thompson and Brown, niles, smooth in 1984 adults smooth smooth elongate flagelli- Haefelfinger, 1963 form denticulate denticulate or smooth flagelliform Marcus and Marcus, 1967

Bouchet, P. 1977. Opisthobranches dc profondeur de I'ocean atlantique: II-Notaspidea et Nudi- branchia. J. Moll. Stud. 43: 28-66. Eliot, C. 1905. The Nudibranchiata of the Scottish National Antarctic Expedition. Rep. Scien. Res. Voyage "Scotia" 1902, 1903, 1904 5: 11-24. Haefelfinger, H. 1963. Remarques biologiques et systematiques au sujet de quelques Tritoniidae de la Mediterranee. Rev. Suisse Zool. 75: 575-583. MacFarland, F. 1966. Studies of opisthobranchiate mollusks of the Pacific coast of North America. Mem. Calif. Acad. Sci. 6: 1-546. Marcus, Er. and Ev. Marcus. 1967. American opisthobranch mollusks. Stud. Trop. Oceanogr. Miami 6: 1-256. Marcus, Ev. 1983. The Western Atlantic Tritoniidae. Bolm. Zool. Univ. S. Paulo 6: 177-214. Odhner, N. 1926. Die Opisthobranchiern. Fur. Res. Swed. Antarc. Exped. 1901-19032(1): 1-100. ---. 1939. Opisthobranchiate from the western and northern coasts of Norway. Kgl. Norske Vidensk. Selsk. Skr. 1939: 1-93. --. 1963. On the of the Family Tritoniidae. Veliger 6: 48-52. Schmekel, L. and A. Portmann. 1982. Opisthobranchia des Mittlemeeres. Nudibranchia und Saco- glossa. Springer-Verlag, Berlin. 410 pp. Tardy, J. 1963. Description d'une nouvelle espece de Tritoniidae, Duvaucelia odhneri, recoItee sur la cote atlantique fran~ise. Bull. Inst. Oceanogr. Monaco 60:1-10. 436 BULLETINOFMARINESCIENCE,VOL.40,NO.3, 1987

Thompson, T. E. 1961. The importance of the larval shell in the classification of the Sacoglossa and Acoela (Gastropoda, Opisthobranchia). Proc. Malac. Soc. Lond. 34: 233-238. ---. 1971. Tritoniidae from the North American Pacific Coast (Mollusca: Opisthobranchia). Veliger 13: 333-338. --- and G. H. Brown. 1984. Biology of opisthobranch molluscs. II. Ray Society, London. 229 pp.

DATEACCEPTED:May 29, 1986.

ADDRESS:Department of Invertebrate Zoology and Geology, California Academy of Sciences, Golden Gate Park, San Francisco, California 94118.